Posters on https://www.tripadvisor.co.uk/ShowTopic-g255055-i120-k11842973-30_31_year_old_working_holiday_visa_417_query-Australia.html and https://www.outback-australia-travel-secrets.com/work-visa-for-30-year-old.html report having received 12 month visas at the age of 30
As noted on the Department's web site on the Working Holiday visa:
Stay longer on a visitor visa
Generally we don't grant a visitor visa after you have been in Australia on a Work and Holiday visa.
If you want to apply for a Visitor visa to stay longer in Australia and the Visitor visa would result in you staying longer than 12 consecutive ...